/*
 * Copyright (C) 2006-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */

package org.alfresco.jlan.server.thread;

import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * Thread Request Queue Class
 *
 * <p>
 * Provides a request queue for a thread pool of worker threads.
 *
 * @author gkspencer
 */
public class ThreadRequestQueue {

	// List of requests

	private Queue<ThreadRequest> m_queue;

	/**
	 * Class constructor
	 */
	public ThreadRequestQueue() {
		m_queue = new LinkedList<ThreadRequest>();
	}

	/**
	 * Return the number of requests in the queue
	 *
	 * @return int
	 */
    public final int numberOfRequests() {
        synchronized (m_queue) {
            return m_queue.size();
        }
    }

	/**
	 * Add a request to the queue
	 *
	 * @param req ThreadRequest
	 */
	public final void addRequest(ThreadRequest req) {

		synchronized ( m_queue) {

			// Add the request to the queue

			m_queue.add(req);

			// Notify a worker that there is a request to process

			m_queue.notify();
		}
	}

	/**
	 * Add requests to the queue
	 *
	 * @param reqList List<ThreadRequest>
	 */
	public final void addRequests(List<ThreadRequest> reqList) {

        synchronized ( m_queue) {

             // Add the requests to the queue
             m_queue.addAll(reqList);
             m_queue.notify();
        }
	}

	/**
	 * Remove a request from the head of the queue
	 *
	 * @return ThreadRequest
	 * @exception InterruptedException
	 */
	public final ThreadRequest removeRequest()
		throws InterruptedException {

		synchronized ( m_queue) {

			// Wait until there is a request

			while ( m_queue.size() == 0)
				m_queue.wait();

			// Get the request from the head of the queue

			return m_queue.poll();
		}
	}

	/**
	 * Wait for a request to be added to the queue
	 *
	 * @exception InterruptedException
	 */
	public final void waitWhileEmpty()
		throws InterruptedException {

		synchronized ( m_queue) {

			// Wait until some work arrives on the queue

			while (m_queue.size() == 0)
				m_queue.wait();
		}
	}

	/**
	 * Wait for the request queue to be emptied
	 *
	 * @exception InterruptedException
	 */
	public final void waitUntilEmpty()
		throws InterruptedException {

		synchronized ( m_queue) {

			// Wait until the request queue is empty

			while (m_queue.size() != 0)
				m_queue.wait();
		}
	}
}
